Trains are complex systems with numerous subsystems, with each subsystem being interdependent on other subsystems. The train's operator is responsible for insuring proper operation of the locomotive and its associated load of passenger or freight cars, including complying with prescribed operating speeds, and assuring that in-train forces remain within acceptable limits. However, the operator cannot usually operate the locomotive so that the fuel consumption is minimized for each trip. For example, factors that must be considered may include emission output, environmental conditions like noise/vibration, a weighted combination of fuel consumption and emissions output, etc. This is difficult to do since, as an example, the size and loading of trains vary, locomotives and their fuel/emissions characteristics are different, and weather and traffic conditions vary.
To address this problem, it is known to provide a train with a computer-implemented system which monitors multiple vehicle parameters and determines the best way to operate the train so as to optimize fuel consumption. Such as system is described in U.S. Patent Application Publication 2007/0225878, entitled “Trip Optimization System and Method for a Train”, assigned to the assignee of the present invention.
To save fuel, optimization systems such as those described in the '878 Publication normally avoid braking a train as much as practical. For example, when a train is going to slow or stop ahead, or pass through a turnout switch to another track at a reduced speed, the optimization system will begin slowing very early by coasting down to the stop or reduced speed location. Additionally, the optimization system may operate a train at a reduced speed for fuel savings whenever that train's schedule allows.
There are often circumstances where a priority need arises to move out of the way of a second train or trains for operational needs. For example, a train may be changing from one track to a second track through a turnout with an allowable speed of 40 mph. A following or opposing second train cannot pass the turnout location on the first track until the first train has cleared completely through the turnout. In this case, the normal operation of the optimization system might plan to move through the turnout at 10 mph instead of 40 mph for fuel savings, and would interfere with the operational need for high speed.